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| United States Patent |
6,071,249
|
|
Cunningham
, et al.
|
June 6, 2000
|
Method and apparatus for obtaining blood for diagnostic tests
Abstract
Method and apparatus for obtaining a sample of blood from a patient for
subsequent diagnostic tests, e.g., glucose monitoring. In one aspect of
the invention, the method comprises the steps of:
(a) forming an unobstructed opening in the area of the skin from which the
sample of blood is to be extracted; and
(b) extracting the sample of blood from the unobstructed opening in the
skin, with the aid of a vacuum and a stretching of the skin.
In another aspect of the invention, an apparatus for carrying out the
method described previously is provided. The apparatus comprises:
(a) a device for forming an unobstructed opening in an area of skin from
which said sample is to be extracted, preferably a lancing assembly; and
(b) a vacuum pump.
Preferably, the apparatus also includes a housing.
It has also been discovered that an improved design and construction of the
nosepiece can provide enhanced collection of blood from the unobstructed
opening in the skin. It has been discovered that by controlling the
construction of the interior cavity of the nosepiece, collection of blood
can be improved.
| Inventors:
|
Cunningham; David D. (Lake Villa, IL);
Henning; Timothy P. (Vernon Hills, IL);
Shain; Eric B. (Glencoe, IL);
Young; Douglas F. (Grayslake, IL);
Lowery; Michael G. (Wildwood, IL);
Graham; Hugh W. (Gurnee, IL)
|
| Assignee:
|
Abbott Laboratories (Abbott Park, IL)
|
| Appl. No.:
|
982324 |
| Filed:
|
December 2, 1997 |
| Current U.S. Class: |
600/578; 606/181 |
| Intern'l Class: |
A61B 005/00 |
| Field of Search: |
600/584,583,578
606/181
|
References Cited
U.S. Patent Documents
| 4577630 | Mar., 1986 | Nitzsche et al.
| |
| 4640297 | Feb., 1987 | Bates.
| |
| 4653513 | Mar., 1987 | Dombrowski.
| |
| 5037431 | Aug., 1991 | Summers et al.
| |
| 5201324 | Apr., 1993 | Swierczek.
| |
| 5320607 | Jun., 1994 | Ishibashi.
| |
| 5368047 | Nov., 1994 | Suzuki et al. | 606/181.
|
| 5680872 | Oct., 1997 | Sesekuro et al. | 600/583.
|
| 5951493 | Sep., 1999 | Douglas et al. | 606/181.
|
| Foreign Patent Documents |
| 0021798 | Jan., 1981 | EP.
| |
| 0212906 | Mar., 1987 | EP.
| |
| 0230472 | Aug., 1987 | EP.
| |
| 0254203 | Jan., 1988 | EP.
| |
| 0371503 | Jun., 1990 | EP.
| |
| 0449525 | Oct., 1991 | EP.
| |
| 0520296 | Dec., 1992 | EP.
| |
| 0575952 | Dec., 1993 | EP.
| |
| 0671146 | Sep., 1995 | EP.
| |
| 0797951 | Oct., 1997 | EP.
| |
| 2803345 | Jun., 1979 | DE.
| |
| 3708031 | Nov., 1987 | DE.
| |
| 2222251 | Feb., 1990 | GB.
| |
| 9109139 | Jun., 1991 | WO.
| |
| 9202175 | Feb., 1992 | WO.
| |
| 9215863 | Sep., 1992 | WO.
| |
| 9303673 | Mar., 1993 | WO.
| |
| 9409713 | May., 1994 | WO.
| |
| 9637148 | Nov., 1996 | WO.
| |
Primary Examiner: Hindenburg; Max
Assistant Examiner: Wingood; Pamela L.
Attorney, Agent or Firm: Weinstein; David L.
Parent Case Text
This application is a continuation-in-part of U.S. Ser. No. 08/759,698,
filed Dec. 6, 1996 and a continuation-in-part of U.S. Provisional
Application No. 60/036,395, filed Jan. 24, 1997.
Claims
What is claimed is:
1. A nosepiece suitable for use with a vacuum aided blood vacuum aided
collection apparatus, said nosepiece comprising:
(a) a lower base having an opening therein;
(b) an upper base having an opening therein;
(c) an interior wall joining said upper base and said lower base, the area
of said opening in said upper base being less than the area of said
opening in said lower base; and
(d) a seal attached to said lower base of said nosepiece, the distance
between the lowermost point of said seal and the lowermost point of said
upper base be such that skin, when stretched into said nosepiece, comes as
close as possible to said upper base or contacts said upper base.
2. The nosepiece of claim 1, further including at least one passageway for
vacuum.
3. The nosepiece of claim 1, wherein said opening in said upper base is
circular in shape.
4. The nosepiece of claim 1, wherein said opening in said upper base is
oval in shape.
5. The nosepiece of claim 1, wherein said interior wall is tapered.
6. The nosepiece of claim 1, wherein said interior wall is comprised of
stepwise cylindrical sections.
7. A nosepiece suitable for use with a vacuum aided blood collection
apparatus, said nosepiece comprising:
(a) a lower base having an opening therein;
(b) an upper base having an opening therein;
(c) an interior wall joining said upper base and said lower base, the area
of said opening in said upper base being less than the area of said
opening in said lower base, wherein said opening in said upper base is
surrounded by a rim; and
(d) a seal attached to said lower base of said nosepiece, the distance
between the lowermost point of said seal and the lowermost point of said
rim be such that skin, when stretched into said nosepiece, comes as close
as possible to said rim or contacts said rim.
8. The nosepiece of claim 1, further including a seal attached to said
lower base of said nosepiece.
9. The nosepiece of claim 8, wherein said seal is in the form of an annular
ring.
10. A nosepiece suitable for use with a vacuum aided blood collection
apparatus, said nosepiece comprising:
(a) a lower base having an opening therein;
(b) an upper base having an opening therein; and
(c) an interior wall joining said upper base and said lower base, the area
of said opening in said upper base being less than the area of said
opening in said lower base, further including a seal attached to said
lower base of said nosepiece, wherein said seal is capable of moving
between a first position and a second position.
11. The nosepiece of claim 8, wherein said seal is formed from rubber or an
elastomeric material.
12. The nosepiece of claim 8, wherein said seal is formed from an adhesive.
13. The nosepiece of claim 1, wherein the ratio of the diameter of the
opening in the lower base to the diameter of the opening in the upper base
is at least about 3 to 1.
14. The nosepiece of claim 1, wherein the distance between the lowermost
point of said seal and the lowermost point of said upper base ranges from
about 1.5 mm to about 8.0 mm.
15. The nosepiece of claim 7, further including at least one passageway for
vacuum.
16. The nosepiece of claim 7, wherein said opening in said upper base is
circular in shape.
17. The nosepiece of claim 7, wherein said opening in said upper base is
oval in shape.
18. The nosepiece of claim 7, wherein said interior wall is tapered.
19. The nosepiece of claim 7, wherein said interior wall is comprised of
stepwise cylindrical sections.
20. The nosepiece of claim 7, wherein said seal is in the form of an
annular ring.
21. The nosepiece of claim 7, wherein said seal is formed from rubber or an
elastomeric material.
22. The nosepiece of claim 7, wherein said seal is formed from an adhesive.
23. The nosepiece of claim 7, wherein the ratio of the diameter of the
opening in the lower base to the diameter of the opening in the upper base
is at least about 3 to 1.
24. The nosepiece of claim 7, wherein the distance between the lowermost
point of said seal and the lowermost point of said rim ranges from about
1.5 mm to about 8.0 mm.
25. The nosepiece of claim 10, further including at least one passageway
for vacuum.
26. The nosepiece of claim 10, wherein said opening in said upper base is
circular in shape.
27. The nosepiece of claim 10, wherein said opening in said upper base is
oval in shape.
28. The nosepiece of claim 10, wherein said interior wall is tapered.
29. The nosepiece of claim 10, wherein said interior wall is comprised of
stepwise cylindrical sections.
30. The nosepiece of claim 10, wherein said seal is formed from rubber or
an elastomeric material.
31. The nosepiece of claim 10, wherein said seal is formed from an
adhesive.
32. The nosepiece of claim 10, wherein the ratio of the diameter of the
opening in the lower base to the diameter of the opening in the upper base
is at least about 3 to 1.
Description
CROSS REFERENCES TO COPENDING APPLICATIONS
This application relates to three patent applications, METHOD AND APPARATUS
FOR OBTAINING BLOOD FOR DIAGNOSTIC TESTS, Attorney's Docket No.
6005.US.P1, METHOD AND APPARATUS FOR OBTAINING BLOOD FOR DIAGNOSTIC TESTS,
Attorney's Docket No. 6005.US.P2, METHOD AND APPARATUS FOR OBTAINING BLOOD
FOR DIAGNOSTIC TESTS, Attorney's Docket No. 6005.US.P4, filed on evendate
herewith The specifications, drawings, and claims of these applications
are incorporated herein by reference. All of the foregoing applications
are commonly owned by the assignee of this invention.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for obtaining samples of
blood for diagnostic purposes.
2. Discussion of the Art
The prevalence of diabetes has been increasing markedly in the world. At
this time, diagnosed diabetics represented about 3% of the population of
the United States. It is believed that the total actual number of
diabetics in the United States is over 16,000,000. Diabetes can lead to
numerous complications, such as, for example, retinopathy, nephropathy,
and neuropathy.
The most important factor for reducing diabetes-associated complications is
the maintenance of an appropriate level of glucose in the blood stream.
The maintenance of the appropriate level of glucose in the blood stream
may prevent and even reverse many of the effects of diabetes.
Glucose monitoring devices of the prior art have operated on the principle
of taking blood from an individual by a variety of methods, such as by
needle or lancet. An individual then coats a paper strip carrying
chemistry with the blood, and finally insert the blood-coated strip into a
blood glucose meter for measurement of glucose concentration by
determination of change in reflectance.
The medical apparatus of the prior art for monitoring the level of glucose
in the blood stream required that an individual have separately available
a needle or lancet for extracting blood from the individual, strips
carrying blood chemistry for creating a chemical reaction with respect to
the glucose in the blood stream and changing color, and a blood glucose
meter for reading the change in color indicating the level of glucose in
the blood stream. The level of blood glucose, when measured by a glucose
meter, is read from a strip carrying the blood chemistry through the
well-known process of reading reflectometers for glucose oxidation.
Generally lancets comprise a blade and a pressable end opposed thereto,
with the blade having an acute end capable of being thrust into skin of a
human. By striking the pressable portion, the acute end of the blade will
pierce the skin, for example, of the finger. The finger lancet is
primarily used to obtain small volumes of blood, i.e., less than 1 mL.
Diabetics use the finger lancet to obtain volumes of blood less than 25
.mu.L for analysis for glucose. A small amount of blood for the blood test
will ooze out of the skin. There are many small blood vessels in each
finger so that a finger can be squeezed to cause a larger drop of blood to
ooze. The finger is one of the most sensitive parts of the body;
accordingly, the finger lancet leads to even more pain than what would be
experienced by extracting blood via lancet at a different body site. The
finger lancet presents another problem because of the limited area
available on the fingers for lancing. Because it is recommended that
diabetics monitor their blood glucose levels four to six times per day,
the limited area on the fingers calls for repeated lancing of areas that
are already sore. Because fingers are sensitive to pain, it is a recent
tendency that the arm is subjected to blood sampling. See, for example,
U.S. Pat. No. 4,653,513. The device of U.S. Pat. No. 4,653,513 comprises a
cylindrical housing and a lancet support, which has a gasket or flexible
portion slidably accommodated in the housing. Springs will retract the
lancet support to thereby reduce air pressure in the housing so that it
sucks a blood sample, automatically and immediately after a lancet pierces
the skin. See also U.S. Pat. No. 5,320,607, which discloses a device
comprising a sealed vacuum chamber in a state of preexisting reduced
pressure, a support member for the sealed vacuum chamber, the support
member defining a suction portion adjacent the sealed vacuum chamber, the
suction portion, in cooperation with the sealed vacuum chamber, exposing
an area of the skin of a patient to a reduced pressure state when the
device is actuated, and means arranged within the suction portion for
slightly rupturing a portion of the area of skin of the patient exposed to
the reduced pressure state.
Because the blood volume requirements for a standard glucose test strip is
typically 3 .mu.L or more, an area of the body that can generate that much
blood from a lancet wound must be used. It is believed, however, that
improvements in glucose test strip technology will reduce the volume of
blood needed to 1 to 3 .mu.L. Because the finger is well supplied with
blood and the amount of blood can be increased by squeezing the finger
after lancing, the finger is the currently preferred body site for
lancing, even though lancing of the finger is painful.
A less painful technique for obtaining body fluids could be found if a
reliable method were found for lancing a body part that is less sensitive
to pain than the finger and obtaining a useful amount of blood from that
body part. A body part such as the forearm is much less sensitive to pain
than the finger, but the amount of blood resulting from the lancing
procedure is generally of an inadequate volume for use with current
detection technology. Ways of increasing blood flow to the finger are
common knowledge. The recommendation is made to diabetics to run their
finger under hot water prior to lancing to improve the blood flow in the
finger and the amount of blood collected from the finger. Running hot
water over a body part to improve blood flow is impractical for areas such
as the forearm or thigh. The availability of hot water is also a concern.
It would be desirable to develop a technique and apparatus for obtaining
blood for diagnostic purposes in a painless, reliable manner.
SUMMARY OF THE INVENTION
This invention provides a method and apparatus for extracting a sample of
blood from a patient for subsequent diagnostic tests, e.g., glucose
monitoring. In one aspect of the invention, the method comprises the steps
of:
(a) forming an unobstructed opening in the area of the skin from which the
sample of blood is to be extracted; and
(b) extracting the sample of blood from the unobstructed opening in the
skin, with the aid of vacuum and stretching of the skin.
In a preferred embodiment of the method, step (a) is preceded by the step
of increasing the availability of blood in the portion of the skin from
which the sample is to be extracted. In this preferred embodiment, the
availability of blood in the portion of the skin from which the sample is
to be extracted can be increased by means of a vacuum, which is applied to
the surface of the skin in the vicinity of the opening prior to forming
the opening in the skin. The vacuum causes the portion of the skin in the
vicinity of the blood extraction site to become engorged with blood. The
vacuum also causes the portion of the skin in the vicinity of the blood
extraction site to become stretched. An opening in this stretched portion
of skin can be formed with a cutting or puncturing device, e.g., a lancet,
or other device capable of forming an opening in the skin, e.g., a laser
or a fluid jet. If a cutting or puncturing device is used to form the
opening, it must be retracted from the opening prior to the step of
extracting the sample of blood from the opening. This retraction will
allow the unrestricted flow of blood through the opening. After the
opening is formed, a vacuum is used to aid in extracting the sample of
blood from the opening in the skin. The sample can be analyzed from the
drops of blood that collect on the surface of the skin at the site of the
opening by applying the blood directly to a glucose detector. It is
preferred, however, that the sample be collected in such a manner, e.g.,
via a capillary tube, that it can be analyzed by conventional diagnostic
devices, such as, for example, a biosensor. In another preferred
embodiment, the sample can be collected in a collection zone that is
integrated with a conventional diagnostic device, e.g., a biosensor.
In an alternative of the aforementioned preferred embodiment, the
availability of blood in the area of the skin from which the sample is to
be extracted can be increased by means of applying thermal energy to that
area of skin. The thermal energy causes the blood in that area of the skin
to flow more rapidly, thereby allowing more blood to be collected per
given unit of time. In this alternative embodiment, steps (a) and (b) can
be carried out in the same manner as they were carried out in the
aforementioned preferred embodiment.
In another aspect of the invention, an apparatus for collecting a sample of
body fluid for analysis in a diagnostic test, e.g., blood, is provided. In
a preferred embodiment, the apparatus comprises:
(a) a housing;
(b) a device for forming an unobstructed opening in an area of skin from
which said sample is to be extracted, preferably a lancing assembly; and
(c) a vacuum pump.
It is also possible to dispense with the housing. However, the housing is
preferred for the convenience of the patient and the protection of the
components.
The vacuum pump requires a source of power. If the apparatus includes a
housing, the source of power can be disposed within the housing.
Alternatively, the source of power can be external to the housing.
The preferred device for forming an unobstructed opening in the area of the
skin from which the sample of blood is to be extracted is a lancing
assembly, which comprises a lancet for forming an opening in the skin.
Alternatively, the unobstructed opening in the skin can be formed by a
laser or a fluid jet.
The vacuum pump can serve the dual purposes of (1) stretching the skin and
(2) enhancing the extraction of the sample of blood from the unobstructed
opening in the skin. Preferably, the vacuum pump can serve the triple
purposes of (1) stretching the skin, (2) increasing the availability of
blood to the area of the skin from which the sample is to be extracted,
and (3) enhancing the extraction of the sample of blood from the
unobstructed opening in the skin. Preferably, the housing further contains
electronics having programmed instructions to switch the vacuum pump on
and off to maintain the desired level of vacuum.
The apparatus preferably contains valves, such as, for example, solenoid
valves, for triggering the lancet of the lancing assembly and releasing
the vacuum at the conclusion of the blood extraction procedure. The
apparatus can optionally contain a heating element to increase the
availability of blood to the area of the skin from which the sample is to
be extracted. The apparatus can also contain a glucose detector integrated
with the apparatus, e.g., a biosensor, to analyze the sample of blood
collected by the apparatus.
The method and apparatus of this invention provide several advantages over
the methods and apparatus of the prior art. First, a sufficient amount of
blood can be extracted from parts of the body, other than the finger, for
conducting glucose monitoring tests. Second, by rendering other parts of
the body suitable for extracting blood, the use of a painful finger lance
can be avoided. Third, by increasing the availability of blood at the site
where the blood is to be extracted, the period of time required for
extracting the sample can be reduced. Because of these advantages, the
diabetic patient is more likely to monitor glucose levels in the blood at
the intervals prescribed by his doctor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of the components of a preferred embodiment of the
apparatus of this invention. In this Figure, the cover of the housing is
removed.
FIG. 2 is a schematic diagram illustrating how a vacuum causes a portion of
the skin to become stretched prior to the formation of an opening in the
skin from which the sample of blood is extracted. FIG. 2 also illustrates
the spatial relationship between the nosepiece of lancing assembly and a
glucose detector, e.g., a biosensor.
FIG. 3 is a block diagram illustrating the electronics of the preferred
embodiment.
FIG. 4 is a schematic diagram illustrating an alternative seal for the
vacuum of the device of the present invention.
FIG. 5 is a perspective view of an embodiment of the apparatus of this
invention. In this figure, the housing of the apparatus is open.
FIG. 6 is a perspective view of an embodiment of the apparatus of this
invention. In this figure, the housing of the apparatus is open.
FIG. 7 is a perspective view of an embodiment of the apparatus of this
invention. In this figure, the housing of the apparatus is open.
FIG. 8 is a perspective view of an embodiment of the apparatus of this
invention. In this figure, the housing of the apparatus is open.
FIG. 9 is a perspective view of an embodiment of the apparatus of this
invention. In this figure, the housing of the apparatus is open.
FIG. 10 is a perspective view of an embodiment of the apparatus of this
invention. In this figure, the housing of the apparatus is open.
FIG. 11 is an elevational view of a cross section of a preferred embodiment
of a nosepiece of this invention.
FIG. 12 is a series of elevational views of cross sections of various
embodiments of nosepieces suitable for use in this invention.
FIGS. 13A, 13B, 13C, and 13D are schematic diagrams of the positioning of
the nosepiece of the apparatus of this invention relative to the lancing
assembly, the detection element, and the skin prior to application of
vacuum, during application of vacuum, during lancing, and during blood
collection and analysis, respectively.
FIG. 14 is a series of elevational views of cross sections of various
embodiments of nosepieces suitable for use in this invention.
FIG. 15 is a graph illustrating the effect that various embodiments of
nosepieces have on filling time of a detecting element.
FIG. 16 is a graph illustrating the average time to fill a multiple-layer
element as a function of the nosepiece used.
FIG. 17 is a graph illustrating the percent filled, as a function of the
nosepiece used.
FIG. 18 is a series of elevational views of cross sections and top plan
views of various embodiments of nosepieces suitable for use in this
invention
FIG. 19 is a graph illustrating airflow rate as a function of the nosepiece
used.
FIG. 20 is a graph illustrating the average volume of blood collected as a
function of the material used to make the seal of the nosepiece assembly.
FIG. 21A is an elevational view of a cross section of a preferred
embodiment of a nosepiece of this invention, wherein the seal is in a
first position. FIG. 21B is an elevational view of the nosepiece of FIG.
21A, wherein the seal is in a second position.
DETAILED DESCRIPTION
The embodiments of this invention require the following steps to carry out
the function of obtaining a sample of blood for carrying out a diagnostic
test, e.g., glucose monitoring:
(a) forming an unobstructed opening in the area of the skin from which the
sample of blood is to be extracted; and
(b) extracting the sample of blood from the unobstructed opening in the
skin, with the aid of a vacuum and a stretching of the skin.
The step of forming an unobstructed opening in the area of the skin from
which the sample of blood is to be extracted is carried out by a piercing
device or some other type of device capable of forming an unobstructed
opening in the skin. Piercing devices suitable for this invention include,
but are not limited to, mechanical lancing assemblies. Other type of
device capable of forming an unobstructed opening in the skin include, but
are not limited to, lasers and fluid jets. Other types of devices capable
of forming an unobstructed opening in the skin can be used, and this
disclosure should not be construed so as to be limited to the devices
listed. Mechanical lancing assemblies are well-known in the art. These
assemblies comprise include standard steel lancets, serrated devices, and
multiple tip devices. The lancets can be made from metal or plastic.
Multiple tip devices provide redundancy, which can reduce the number of
failures and increase the volume of blood extracted.
Lasers suitable for forming an unobstructed opening in the skin to draw
blood are also well-known in the art. See for example, U.S. Pat. Nos.
4,775,361, 5,165,418, 5,374,556, International Publication Number WO
94/09713, and Lane et al. (1984) IBM Research Report--"Ultraviolet-Laser
Ablation of Skin", all of which are incorporated herein by reference.
Lasers that are suitable for forming an unobstructed opening in the skin
the skin include Er:YAG, Nd:YAG, and semiconductor lasers.
Fluid jets suitable for forming an unobstructed opening in the skin employ
a high pressure jet of fluid, preferably a saline solution, to penetrate
the skin.
Regardless of what type of device is utilized to form an unobstructed
opening in the skin, the opening formed by the device must be
unobstructed. As used herein, the term "unobstructed" means free from
clogging, hampering, blocking, or closing up by an obstacle. More
specifically, the expressions "unobstructed opening in the area of the
skin from which the sample is to be extracted", "unobstructed opening in
the skin", and the like are intended to mean that the portion of the
opening below the surface of the skin is free from any foreign object that
would clog, hamper, block, or close up the opening, such as, for example,
a needle of any type. For example, if a lancet is used to form the
opening, it must be retracted from the opening prior to the commencement
of the extraction of blood. Because lasers and fluid jets do not require
contact with the skin to form openings in the skin, these types of devices
typically provide unobstructed openings. However, these expressions are
rot intended to include foreign objects at the surface of the skin or
above the surface of the skin, such as, for example, a glucose monitor.
This feature, i.e., the unobstructed opening, can be contrasted with the
opening used in the method and apparatus described in U.S. Pat. No.
5,320,607, in which the piercing and cutting means remains in the skin
during the duration of the period of blood extraction. By leaving the
opening unobstructed, blood can be extracted much more rapidly from the
opening than it would be extracted if the piercing and cutting means were
allowed to remain in the opening. In addition, the requirement of an
unobstructed opening exposes the body to a foreign object either not at
all or for only a very short period of time, which is welcomed by the
patient.
The step of extracting the sample of blood from the opening in the skin is
carried out by a combination of extraction enhancing elements. Extraction
enhancing elements suitable for use in this invention include, but are not
limited to, vacuum, skin stretching elements, and heating elements. It has
seen discovered that when these elements are used in combination, the
volume of blood extracted is greatly increased, particularly when a vacuum
is applied in combination with skin stretching. In this combination, the
vacuum not only causes the blood to be rapidly removed from the
unobstructed opening by suction, it also causes a portion of the skin in
the vicinity of the opening to be stretched. Stretching of the skin can be
effected by other means, such as mechanical means or adhesives. Mechanical
means include devices for pinching or pulling the skin; adhesives bring
about stretching of the skin by means of pulling. It is preferred to use a
vacuum to effect stretching of the skin. Like a vacuum, a heating element
operates more effectively in combination with other techniques, e.g.,
stretching of the skin.
In the preferred embodiment of this invention, step (a), the step of
forming the unobstructed opening, is preceded by the step of increasing
the availability of blood at the area of the skin from which the sample is
to be extracted. The availability of blood at a given area of the skin can
be increased by at least two methods. In one method, a vacuum can be used
to cause blood flowing through blood vessels to pool in the area of the
skin where the vacuum is applied. In another method, heat can be used to
cause blood flowing through blood vessels to flow more rapidly in the area
of the skin where heat is applied, thereby allowing a greater quantity of
blood to be extracted from the blood extraction site per unit of time.
Although the step of increasing the availability of blood in the vicinity
of the blood extraction site is not required, the employment of this step
can result in a greater volume of blood extracted. Elements for increasing
the availability of blood at a blood extraction site that are suitable for
use in this invention include, but are not limited to, vacuum, localized
heating element, skin stretching element, and chemicals. As stated
previously, applying a vacuum to the area of the skin from which blood is
to be extracted can increase blood availability under and within the skin
at the application site. The vacuum can also be used to stretch the skin
upwardly into a chamber, thereby increasing pooling of blood under and
within the skin. This combination of vacuum and skin stretching can be an
extension of the combination used to extract blood from the opening in the
skin, as previously described. It is well-known that heat can increase
perfusion on the large scale of a limb or a finger. Chemical means, such
as histamine, can be used to cause a physiological response to increase
perfusion under and within the skin.
In the preferred embodiments of the invention, the extracted blood is also
collected. The step of collecting the sample of blood can be carried out
in a variety of ways. For example, the blood can be collected in capillary
tubes or absorbent paper. Alternatively, the blood can be allowed to
remain in the lancet assembly, from which it can used directly in a
diagnostic test. Most preferably, the sample of blood is collected on the
application zone of a glucose detector, from where it can be used directly
to provide an indication of the concentration of glucose in the blood.
Regardless of the manner in which the blood sample is collected, the
sample can be analyzed at a time later than the time of collection or at a
location remote from the location of collection or both.
A preferred embodiment of the invention will now be described in detail.
Blood extraction device 10 comprises a housing 12. Disposed within the
housing 12 are a vacuum pump 14, a lancing assembly 16, a battery 18, and
electronics 20. A switch 22 is provided to activate electronics 20.
The housing 12 is preferably made from a plastic material. It is preferably
of sufficient size to contain all of the components that are required for
forming an unobstructed opening in the area of the skin from which the
sample of blood is to be extracted, extracting the sample of blood from
the unobstructed opening in the skin, preferably with the aid of a vacuum
and a stretching of the skin, and collecting the extracted sample in an
amount sufficient to carry out a diagnostic test. Methods of preparing the
housing 12 are well-known to one of ordinary skill in the art. As stated
previously, the housing 12 is not required, but is preferred for the
convenience of the patient and the protection of the components.
The vacuum pump 14 must be capable of providing a vacuum that will provide
sufficient suction to stretch the portion of the skin in the region from
which the sample of blood is to be extracted. Typically, the portion of
stretched skin is raised a distance of 1 to 10 mm, preferably 3 to 5 mm,
from the plane of the body part of which it is a portion. As the suction
provided by the vacuum pump 14 is stretching the appropriate portion of
skin, the suction provided by the vacuum pump 14 also causes the stretched
portion to become engorged with blood. The level of suction provided must
be sufficient to cause a relatively large volume of blood to become
engorged at the point that the vacuum is applied. The vacuum pump 14 must
also be capable of providing sufficient suction to extract blood from the
opening in the skin at a rate sufficient to extract at least 1 .mu.L of
blood within a period of five minutes. A vacuum pump 14 that is suitable
for the device of this invention can be a diaphragm pump, a piston pump, a
rotary vane pump, or any other pump that will perform the required
functions set forth previously. Typically, the vacuum pump 14 employs a
self-contained permanent magnet DC motor. Vacuum pumps that are suitable
for this invention are well-known to those of ordinary skill in the art
and are commercially available. A vacuum pump suitable for use in the
present invention is available from T-Squared Manufacturing Company,
Nutley, N.J., and has the part number T2-03.08.004.
The vacuum pump 14 is preferably capable of providing a pressure of down to
about -14.7 psig, and is more preferably operated at from about -3.0 psig
to about -10.0 psig. The area of the skin subjected to vacuum preferably
ranges up to about 50 cm.sup.2, more preferably from about 0.1 to about
5.0 cm.sup.2. The period of vacuum application prior to forming the
opening in the skin, i.e., for increasing the availability of blood to the
application site, preferably ranges up to about 5 minutes, preferably from
about 1 to about 15 seconds. The period of vacuum application subsequent
to forming the opening in the skin, i.e., for aiding in the extraction of
blood from the unobstructed opening, preferably ranges up to about 5
minutes, preferably from about 1 to about 60 seconds. The vacuum provided
by the vacuum pump 14 can be continuous or pulsed. A continuous vacuum is
preferred for the reason that it requires fewer components than does a
pulsed vacuum. It is preferred that the vacuum applied not cause
irreversible damage to the skin. It is preferred that the vacuum applied
not produce bruises and discolorations of the skin that persist for
several days. It is also preferred that the level of vacuum applied and
duration of application of vacuum not be so excessive that it causes the
dermis to separate from the epidermis, which results in the formation of a
blister filled with fluid.
The vacuum pump feature offers significant advantages over the method and
apparatus described in U.S. Pat. No. 5,320,607, in which a sealed vacuum
chamber in a state of preexisting reduced pressure is used. The use of a
vacuum pump provides the user with greater control of blood extraction
conditions than does a sealed vacuum chamber in a state of preexisting
reduced pressure. For example, if the vacuum is insufficient, energy can
be provided to the vacuum pump to bring about a higher level of vacuum,
thereby providing greater suction.
The lancing assembly 16 comprises at least one lancet. Standard lancets can
be used in the lancing assembly of this invention. Narrow gauge (28 to 30
gauge) lancets are preferred. Lancets suitable for this invention can be
made from metal or plastic. Lancets suitable for this invention can have
single points or multiple points. The depth of penetration of the lancet
preferably ranges from about 0.4 to about 2.5 mm, more preferably from
about -0.4 to about 1.6 mm. The length of the lancet or lancets preferably
ranges from about 1 mm to about 5 mm. The lancing assembly is preferably
located so that the user can easily replace used lancets. The lancet of
the lancing assembly 16 can be cocked manually or automatically, e.g., by
means of a vacuum-actuated piston or diaphragm. The lancet of the lancing
assembly 16 can be triggered by manually or automatically, e.g., by means
of a vacuum-actuated piston or diaphragm.
Lancing assemblies are well-known in the art. Representative examples of
lancing assemblies suitable for this invention are described in U.S. Pat.
Nos. Re. 32,922, 4,203,446, 4,990,154, and 5,487,748, all of which are
incorporated herein by reference. A particularly suitable lancing assembly
for this invention is described in U.S. Pat. No. Re. 32,922. However, any
lancing assembly selected should operate in conjunction with the other
features of the apparatus of this invention. For example, if a vacuum is
employed, the lancing assembly must be designed so that a vacuum can be
formed and drawn through the assembly. The lancing assembly can be
designed to allow automatic cocking and automatic triggering of the
lancet.
The vacuum pump 14 is connected to the lancing assembly 16 by an evacuation
tube 24. The air that is evacuated from the lancing assembly 16 by the
vacuum pump 14 is removed via the evacuation tube 24. The evacuation tube
24 is typically made from a polymeric material. A check valve 20 is placed
between the vacuum pump 14 and the lancing assembly 16 at a point in the
evacuation tube 24 to prevent air removed from the lancing assembly 16 by
the vacuum pump 14 from flowing back to the lancing assembly 16 and
adversely affecting the vacuum.
A source of power for the vacuum pump 14 can be disposed within the housing
12. A source of power suitable for the device of this invention is a
battery 18. Alternatively, an external source of power can be used to
operate the vacuum pump 14. The power source is actuated by the
electronics 20, which, in turn, is actuated by the switch 22.
The electronics 20 may incorporate a microprocessor or microcontroller. The
function of the electronics 20 is to switch power on and off to operate
the various components in the apparatus. These components include, but are
not limited to, the vacuum pump 14. The electronics 20 can also be use to
switch power on and off to operate components in alternative embodiments,
e.g., heating elements, lancets, indicating devices, and valves.
Electronics suitable for this invention is the "TATTLETALE MODEL 5F"
controller/data logger, commercially available from Onset Computer
Corporation, 536 MacArthur Blvd. P.O. Box 3450, Pocasset, Mass.
02559-3450. Auxiliary electronic devices, such as power transistors,
pressure monitors, and OP-Amps (operational amplifiers), may also be
required in order to provide an interface between the controller and the
operational components. All electronics required for this invention are
well-known to one of ordinary skill in the art and are commercially
available. Auxiliary electronic devices suitable for use in this invention
include the following components:
______________________________________
Component Source Catalog Number
______________________________________
Mosfet Drivers
International Rectifier
IRLD024
El Segundo, CA
Op-Amp National Semiconductor
LM358
Santa Clara, CA
Status LED Hewlett-Packard HLMPD150
Newark Electronics
Schaumburg, IL
Pressure Sensor
Sensym, Inc. SDX15D4
Milpitas, CA
______________________________________
FIG. 3 illustrates by way of a block diagram how the foregoing electronic
components can be arranged to carry out the method of the present
invention.
Operation of the blood extraction device 10 will now be described.
Referring now to FIGS. 1, 2 and 3, the nosepiece 30 of the lancing
assembly 16 is applied to the surface of the skin, designated herein by
the letter "S". The end of the nosepiece 30 that contacts the skin is
equipped with a seal 32. The purpose of the seal 32 is to prevent air from
leaking into blood extraction chamber 34, so that the vacuum pump 14 can
provide sufficient suction action for increasing the availability of blood
to the area of the skin from which the sample is to be extracted,
stretching the skin, and extracting the sample of blood from the
unobstructed opening in the skin. The seal 32 surrounds an opening 33 in
the nosepiece 30. The opening 33 in the nosepiece allows communication
between the surface of the skin and a blood extraction chamber 34 in the
nosepiece 30. The seal 32 is preferably made of a rubber or an elastomeric
material. FIG. 4 illustrates an alternative position for the seal 32. In
FIG. 4, the seal is designated by the reference numeral 32'. The remaining
parts of FIG. 4 are the same as those of FIG. 2, and, accordingly, retain
the same reference numerals as were used in FIG. 2.
It has been discovered that an improved design and construction of the
nosepiece 30 can provide enhanced collection of blood from the
unobstructed opening in the skin. In FIG. 2, it is shown that the interior
walls of the nosepiece form a shape that is essentially cylindrical. While
this design is capable of providing adequate performance in the method of
this invention, it has been discovered that by changing the construction
of the interior cavity of the nosepiece, collection of blood can be
accelerated.
A nosepiece assembly 3000 is illustrated in FIG. 11. The nosepiece assembly
3000 comprises a nosepiece 3001 and a seal 3002. The nosepiece 3001
comprises a lower base 3004 having an opening 3005 therein. Above the
lower base 3004 is an upper base 3006 having an opening 3007 therein. The
features of the exterior of the nosepiece, other than the lower base 3004
and the upper base 3006, are not critical to this invention, and one of
ordinary skill in the art can design the exterior walls of the nosepiece
in any manner that does not adversely affect the operation of the
nosepiece of this invention. The features of the interior of the
nosepiece, the lower base 3004, the upper base 3006, and, in some cases,
the seal 3002 are critical and, consequently, they will be described in
greater detail. An interior wall 3008 encloses a cavity 3010 of the
nosepiece 3001. It is critical that the interior wall 3008 of the
nosepiece 3001 be structured in such a manner that the opening 3007 in the
upper base 3006 be of an equal or smaller area than the opening 3005 in
the lower base 3004. It is desired that the area of the opening 3007 be
reduced to as small of a size as possible, but not so small as to
interfere with the collection of blood by a glucose monitor (see FIG. 2)
or with the path of a lancet. An optional rim 3012 can surround the
opening 3007 in the upper base 3006.
There a several ways of causing the area of the opening 3007 to be less
than the area of the opening 3005. As shown in FIG. 11, the interior wall
3008 can be tapered so as to bring about a reduction in the area of the
opening 3007. The tapering can begin at any point along the interior wall
3008 of the nosepiece 3001. If the tapered portion runs all the way from
the beginning of the tapered portion to the upper base 3006, the optional
rim 3012 still have a depth of zero, and thus be eliminated from the
nosepiece. Alternatively, the area of the opening 3007 can merely be made
smaller than the area of the opening 3005, such as through the use of
step-wise cylindrical sections.
Ports 3014 and 3016 can be included in the nosepiece 3001 to give the
cavity 3010 more exposure to a vacuum, if needed.
In order to more accurately describe the construction of the nosepiece
assembly 3000, reference points, designated by alphabetical letters, have
been placed on FIG. 11 so that typical distances between these reference
points can be disclosed. The optional rim 3012 has a depth designated by
the line "ab". This depth typically ranges from 0 to about 1.5 mm,
preferably from 0 to about 1.0 mm. The opening 3007 in the upper base 3006
has a major dimension designated by the line "cd". The area of the opening
3007 typically ranges from about 1 to about 500 mm.sup.2, preferably from
about 1 to about 150 mm.sup.2. The opening 3005 in the lower base 3004 has
a major dimension designated by the line "ef". The area of the opening
3005 typically ranges from about 10 to about 500 mm.sup.2, preferably from
about 50 to about 150 mm.sup.2. The distance from the lowermost point of
the rim 3012 to to lowermost point of the seal 3002 (hereinafter
"rim-to-seal distance") is designated by the line "bg". This distance
typically ranges from about 1.5 to about 8.0 mm, preferably from about 3
to about 6 mm. It is preferred that the distance be selected so that the
skin, when stretched into the nosepiece 3001, comes as close as possible
to the rim 3012 or the upper base 3006 of the nosepiece 3001. If the rim
3012 is not present, the point "d" will be located at the level of the
upper base 3006. The thickness of the seal 3002 is represented by the line
"eh". The width of the sealing surface and the width of the sealed surface
of the lower base 3004 are designated by the line "hj". One of ordinary
skill in the art would have sufficient expertise to optimize the
dimensions of the nosepiece without undue experimentation. Additional
details regarding the nosepiece 3001 and the seal 3002 are dealt with in
the examples.
This improved nosepiece has several advantages. The improved design and
construction of the nosepiece can provide enhanced collection of blood
from the unobstructed opening in the skin. The nosepiece brings about a
better seal to the body than do the nosepieces previously used. A better
seal reduces the amount of vacuum leakage, with the result that a less
expensive vacuum pump can be used. In addition, the improved nosepiece
allows a seal to be maintained on those individuals having excessively
hairy skin.
The switch 22 is actuated, typically by being pressed, thereby activating
the electronics 20, which starts the vacuum pump 14. The vacuum pump 14
then provides a suction action. The suction action of the vacuum pump 14
causes the skin circumscribed by the seal 32 to become engorged with
blood. Engorgement of the skin with blood is accompanied by a stretching
of and rising up of the skin up to opening 33.
After an appropriate period of time, which is typically pre-set by the
programmer of the electronics, the lancing assembly 16 is triggered,
thereby causing the lancet 36 to penetrate the skin that has risen up to
the opening 33 and that is engorged with blood. The lancet 36 is
preferably triggered automatically, by a solenoid valve 38 that causes a
vacuum-actuateed piston (not shown) to trigger the lancet 36. The lancet
36 is then retracted, preferably automatically. Thereupon, the blood flows
out of the unobstructed opening resulting from the lancet 36, and, aided
by the vacuum generated by the vacuum pump 14, is collected. When
sufficient blood has been collected or a pre-set time interval has passed,
the electronics 20 causes the vacuum pump 14 to stop. The device 10 can
then be removed from the surface of the skin after another solenoid valve
(not shown because it is hidden under solenoid valve 38) is opened to vent
the vacuum to allow ease of removal of the device from the surface of the
skin. Solenoid valves suitable for use with the apparatus described herein
are commercially available from The Lee Company, Essex, Conn., and have
the part number LHDA0511111H.
The blood is preferably directly collected on the application zone of a
glucose detector, e.g., a reflectance strip or biosensor. The blood can
then be used as the sample for a determination of glucose concentration in
blood. Alternatively, the blood can be collected by other collection
devices, such as, for example, a capillary tube or absorbent paper.
The apparatus of the present invention can include a glucose detector for
analyzing the blood sample extracted by the apparatus. Glucose detectors
are well-known in the art. With respect to glucose monitoring, there are
two major categories of glucose detectors--reflectometers and biosensors.
Representative examples of reflectometers suitable for this invention are
described in U.S. Pat. No. 4,627,445, incorporated herein by reference.
Representative examples of biosensors suitable for this invention are
described in U.S. Pat. No. 5,509,410, incorporated herein by reference.
The glucose detector is preferably disposed in the nosepiece 30 of the
lancing assembly 16. The glucose detector must be located at a position
sufficiently close to the site of blood extraction so that the quantity of
extracted blood collected will be sufficient to carry out a standard
glucose monitoring test. Typically, this distance will preferably be no
more than 5 mm from the site of blood extraction, more preferably no more
than 3 mm from the site of blood extraction, most preferably no more than
1 mm from the site of blood extraction. Care must be taken in the
placement of the glucose detector so that the detector does not adversely
affect the vacuum, when a vacuum is employed to aid in the extraction of
blood. In addition, the glucose detector 40 should be modified, if
necessary, so that the blood collected in the collection zone of the
glucose detector is capable of being used to activate the glucose
detector.
FIG. 2 also illustrates a manner for disposing a glucose detector 40 in the
nosepiece 30 of the lancing assembly 16.
FIGS. 5, 6, 7, 8, 9, and 10 illustrate various alternative embodiments of
the apparatus of this invention. In FIG. 5, blood extraction device 100
comprises a housing 102. The housing 102 is separable into two portions, a
receiving portion 102a and a projecting portion 102b. A gasket 104 is
provided to seal the portions 102a and 102b of the housing 102 and to aid
in separation of the receiving portion 102a from the projecting portion
102b. The receiving portion 102a forms a tight fit with the projecting
portion 102b by means of friction. Projecting elements 102c and 102d are
used to guide the projecting portion 102b into the receiving portion 102a.
Disposed within the housing 102 are a vacuum pump (not shown), a lancing
assembly 108, a battery (not shown), and electronics (not shown). A switch
109 is provided to activate the electronics. The vacuum pump is connected
to the lancing assembly 108 by an evacuation tube (not shown). A check
valve (not shown) is placed between the vacuum pump and the lancing
assembly 108.
During the process of obtaining the sample, the receiving portion 102a and
the projecting portion 102b are fitted tightly together. The area of the
receiving portion 102a of the housing 102 of the device 100 that is to
contact the skin is equipped with a seal 110. The seal 110 surrounds an
opening 112 in the receiving portion 102a. The opening 112 in the
receiving portion 102a allows communication between the surface of the
skin and a blood extraction chamber adjacent to a glucose detector 114,
shown here in the shape of a strip. When in use, the device 100 is
positioned so that the lancing assembly 108 is placed over the region on
the surface of the skin from which the sample is to be obtained. In order
to obtain the sample of blood, the receiving portion 102a of the housing
102 of the device 100 is placed against the skin, whereby the seal 110
allows a satisfactory vacuum to be effected. The switch 109 is actuated,
typically by being pressed, thereby activating the electronics, which
starts the vacuum pump. The vacuum pump then provides a suction action.
The suction action of the vacuum pump causes the skin circumscribed by the
seal 110 to become engorged with blood. Engorgement of the skin with blood
is accompanied by a stretching of and rising up of the skin up to the
opening 112. After an appropriate period of time, which is typically
pre-set by the programmer of the electronics, the lancing assembly 108 is
triggered, thereby causing the lancet 116 to penetrate the skin that has
risen up to the opening 112 and that is engorged with blood. The lancet
116 is preferably triggered automatically, by a solenoid valve (not shown)
that causes a vacuum-actuated piston (not shown) to trigger the lancet
116. The remaining steps of the process relating to collection of a sample
of blood are substantially similar to the steps described in the
embodiment shown in FIGS. 1, 2, 3, and 4.
In the embodiment shown in FIG. 5, the glucose detector 114 is inserted
into a slot 118 in the projecting portion 102b of the housing 102. The
receiving portion 102a of the housing 102 causes the glucose detector 114
to be moved into its proper position for testing. The results obtained
from the glucose detector 114 can be displayed on a screen 120, typically
a conventional liquid crystal digital display. The receiving portion 102a
is separated from the projecting portion 102b when the lancet 116 or
glucose detector 114 is being replaced. The receiving portion 102a is
fitted tightly to the projecting portion 102b during the process of
obtaining a sample of blood.
The relative positions of the vacuum pump, the battery, the electronics,
the evacuation tube, the check valve, the solenoid valves, and the
vacuum-actuated piston are substantially similar to the relative positions
of these components as described in the embodiments shown in FIGS. 1 and
2.
In FIG. 6, blood extraction device 200 comprises a housing 202. The housing
202 comprises a door portion 202a that is attached to the remaining
portion 202b of the housing 202 by a hinge 206. A gasket 207 is provided
to seal the housing 202 when the door portion 202a is closed. The door
portion 202a can be closed by pivoting it around the hinge 206. When the
door portion 202a is closed, the convex portion 202c of the door portion
202a fits precisely into the concave portion 202d of the remaining portion
202b of the housing 202. The remaining edges of the door portion 202a fit
tightly against the remaining edges of the remaining portion 202b of the
housing 202. Disposed within the housing 202 are a vacuum pump (not
shown), a lancing assembly 208, a battery (not shown), and electronics
(not shown). A switch (not shown) is provided to activate the electronics.
The vacuum pump is connected to the lancing assembly 208 by an evacuation
tube (not shown). A check valve (not shown) is placed between the vacuum
pump and the lancing assembly 208.
During the process of obtaining the sample, the door portion 202a is
closed. The area of the door portion 202a of the housing 202 of the device
200 that is to contact the skin is equipped with a seal (not shown). The
seal surrounds an opening 212 in the door portion 202a. The opening 212 in
the door portion 202a allows communication between the surface of the skin
and a blood extraction chamber adjacent to a glucose detector 214, shown
here in the shape of a strip. When in use, the device 200 is positioned so
that the lancing assembly 208 is placed over the region on the surface of
the skin from which the sample is to be obtained. In order to obtain the
sample of blood, the door portion 202a of the housing 202 of the device
200 is placed against the skin, whereby the seal allows a satisfactory
vacuum to be effected. The switch is actuated, typically by being pressed,
thereby activating the electronics, which starts the vacuum pump. The
vacuum pump then provides a suction action. The suction action of the
vacuum pump causes the skin circumscribed by the seal to become engorged
with blood. Engorgement of the skin with blood is accompanied by a
stretching of and rising up of the skin up to the opening 212. After an
appropriate period of time, which is typically pre-set by the programmer
of the electronics, the lancing assembly 208 is triggered, thereby causing
the lancet 216 to penetrate the skin that has risen up to the opening 212
and that is engorged with blood. The lancet 216 is preferably triggered
automatically, by a solenoid valve (not shown) that causes a
vacuum-actuated piston (not shown) to trigger the lancet 216. The
remaining steps of the process relating to collection of a sample of blood
are substantially similar to the steps described in the embodiment shown
in FIGS. 1, 2, 3, and 4.
In the embodiment shown in FIG. 6, the glucose detector 214 is inserted
into slots 218a and 218b of the housing 202. The results obtained from the
glucose detector 214 can be displayed on screen 220, typically a
conventional liquid crystal digital display. The door portion 202a is
opened when the lancet 216 or glucose detector 214 is being replaced. The
door portion 202a is closed during the process of obtaining a sample of
blood.
The relative positions of the vacuum pump, the battery, the electronics,
the switch, the evacuation tube, the check valve, the seal, the solenoid
valves, and the vacuum-actuated piston are substantially similar to the
relative positions of these components as described in the embodiments
shown in FIGS. 1 and 2.
In FIG. 7, blood extraction device 300 comprises a housing 302. The housing
302 comprises a door portion 302a that is attached to the remaining
portion 302b of the housing 302 by a hinge 306. A gasket 307 is provided
to seal the housing 302 when the door portion 302a is closed. The door
portion 302a can be closed by pivoting it around the hinge 306. When the
door portion 302a is closed, the convex portion 302c of the door portion
302a fits precisely into the concave portion 302d of the remaining portion
302b of the housing 302. The remaining edges of the door portion 302a fit
tightly against the remaining edges of the remaining portion 302b of the
housing 302. Disposed within the housing 302 are a vacuum pump (not
shown), a lancing assembly 308, a battery (not shown), and electronics
(not shown). A switch (not shown) is provided to activate the electronics.
The vacuum pump is connected to the lancing assembly 308 by an evacuation
tube (not shown). A check valve (not shown) is placed between the vacuum
pump and the lancing assembly 308.
During the process of obtaining the sample, the door portion 302a is
closed. The area of the door portion 302a of the housing 302 of the device
300 that is to contact the skin is equipped with a seal (not shown). The
seal surrounds an opening 312 in the door portion 302a. The opening 312 in
the door portion 302a allows communication between the surface of the skin
and a blood extraction chamber adjacent to a glucose detector 314, shown
here in the shape of a strip. When in use, the device 300 is positioned so
that the lancing assembly 308 is placed over the region on the surface of
the skin from which the sample is to be obtained. In order to obtain the
sample of blood, the door portion 302a of the housing 302 of the device
300 is placed against the skin, whereby the seal allows a satisfactory
vacuum to be effected. The switch is actuated, typically by being pressed,
thereby activating the electronics, which starts the vacuum pump. The
vacuum pump then provides a suction action The suction action of the
vacuum pump causes the skin circumscribe by the seal to become engorged
with blood. Engorgement of the skin with blood is accompanied by a
stretching of and rising up of the skin up to the opening 312. After an
appropriate period of time, which is typically pre-set by the programmer
of the electronics, the lancing assembly 308 is triggered, thereby causing
the lancet 316 to penetrate the skin that has risen up to the opening 312
and that is engorged with blood. The lancet 316 is preferably triggered
automatically, by a solenoid valve (not shown) that causes a
vacuum-actuated piston (not shown) to trigger the lancet 316. The
remaining steps of the process relating to collection of a sample of blood
are substantially similar to the steps described in the embodiment shown
in FIGS. 1, 2, 3, and 4.
In the embodiment shown in FIG. 7, the glucose detector 314 is inserted
into a slot 318 of the housing 302. The results obtained from the glucose
detector 314 can be displayed on screen 320, typically a conventional
liquid crystal digital display. In FIG. 7, connections 322 for the
electronics are shown. The door portion 302a is opened when the lancet 316
or glucose detector 314 is being replaced. The door portion 302a is closed
during the process of obtaining a sample of blood.
The relative positions of the vacuum pump, the battery, the electronics,
the switch, the evacuation tube, the check valve, the seal, the solenoid
valves, and the vacuum-actuated piston are substantially similar to the
relative positions of these components as described in the embodiments
shown in FIGS. 1 and 2.
In FIG. 8, blood extraction device 400 comprises a housing 402. The housing
402 comprises a door portion 402a that is attached to the remaining
portion 402b of the housing 402 by a hinge 406. A gasket 407 is provided
to seal the housing 402 when the door portion 402a is closed. The door
portion 402a can be closed by pivoting it around the hinge 406. When the
door portion 402a is closed, the convex portions 402c and 402d of the door
portion 402a fit precisely into the concave portions 402e and 402f,
respectively, of the remaining portion 402b of the housing 402. The
remaining edges of the door portion 402a fit tightly against the remaining
edges of the remaining portion 402b of the housing 402. Disposed within
the housing 402 are a vacuum pump (not shown), a lancing assembly 408, a
battery (not shown), and electronics (not shown). A switch 409 is provided
to activate the electronics. The vacuum pump is connected to the lancing
assembly 408 by an evacuation tube (not shown). A check valve (not shown)
is placed between the vacuum pump and the lancing assembly 408.
During the process of obtaining the sample, the door portion 402a is
closed. The area of the door portion 402a of the housing 402 of the device
400 that is to contact the skin is equipped with a seal (not shown). The
seal surrounds an opening 412 in the door portion 402a. The opening 412 in
the door portion 402a allows communication between the surface of the skin
and a blood extraction chamber adjacent to a glucose detector 414, shown
here in the shape of a strip. When in use, the device 400 is positioned so
that the lancing assembly 408 is placed over the region on the surface of
the skin from which the sample is to be obtained. In order to obtain the
sample of blood, the door portion 402a of the housing 402 of the device
400 is placed against the skin, whereby the seal allows a satisfactory
vacuum to be effected. The switch 409 is actuated, typically by being
pressed, thereby activating the electronics, which starts the vacuum pump.
The vacuum pump then provides a suction action. The suction action of the
vacuum pump causes the skin circumscribed by the seal to become engorged
with blood. Engorgement of the skin with blood is accompanied by a
stretching of and rising up of the skin up to the opening 412. After an
appropriate period of time, which is typically pre-set by the programmer
of the electronics, the lancing assembly 408 is triggered, thereby causing
the lancet 416 to penetrate the skin that has risen up to the opening 412
and that is engorged with blood. The lancet 416 is preferably triggered
automatically, by a solenoid valve (not shown) that causes a
vacuum-actuated piston (not shown) to trigger the lancet 416. The
remaining steps of the process relating to collection of a sample of blood
are substantially similar to the steps described in the embodiment shown
in FIGS. 1, 2, 3, and 4.
In the embodiment shown in FIG. 8, the glucose detector 414 is inserted
into a slot 418 of the housing 402. In this embodiment, it is shown that
glucose detector 14 can be rotated 90.degree. between two positions to
simplify insertion and replacement thereof. The results obtained from the
glucose detector 414 can be displayed on screen 420, typically a
conventional liquid crystal digital display. The door portion 402a is
opened when the lancet 416 or glucose detector 414 is being replaced. The
door portion 402a is closed during the process of obtaining a sample of
blood.
The relative positions of the vacuum pump, the battery, the electronics,
the evacuation tube, the check valve, the seal, the solenoid valves, and
the vacuum-actuated piston are substantially similar to the relative
positions of these components as described in the embodiments shown in
FIGS. 1 and 2.
In FIG. 9, blood extraction device 500 comprises a housing 502. The housing
502 comprises a cover portion 502a that is attached to the remaining
portion 502b of the housing 502 by a hinge 506. A gasket 507 is provided
to seal the housing 502 when the cover portion 502a is closed. The cover
portion 502a can be closed by pivoting it around the hinge 506. When the
cover portion 502a is closed, edges 502c of the cover portion 502a tightly
fit against edges 502d of the remaining portion 502b of the housing 502.
Disposed within the housing 502 are a vacuum pump (not shown), a lancing
assembly 508, a battery (not shown), and electronics (not shown). A switch
(not shown) is provided to activate the electronics. The vacuum pump is
connected to the lancing assembly 508 by an evacuation tube (not shown). A
check valve (not shown) is placed between the vacuum pump and the lancing
assembly 508.
During the process of obtaining the sample, the cover portion 502a is
closed. The cover portion 502a of the housing 502 of the device 500 that
is to contact the skin is equipped with a seal 511. The seal 511 surround
an opening 512 in the cover portion 502a. The opening 512 in the cover
portion 502a allows communication between the surface of the skin and a
blood extraction chamber adjacent to a glucose detector 514, shown here in
the shape of a strip. When in use, the device 500 is positioned so that
the lancing assembly 508 is placed over the region on the surface of the
skin from which the sample is to be obtained. In order to obtain the
sample of blood, the cover portion 502a of the housing 502 of the device
500 is placed against the skin, whereby the seal allows a satisfactory
vacuum to be effected. The switch is actuated, typically by being pressed,
thereby activating the electronics, which starts the vacuum pump. The
vacuum pump then provides a suction action. The suction action of the
vacuum pump causes the skin circumscribed by the seal to become engorged
with blood. Engorgement of the skin with blood is accompanied by a
stretching of and rising up of the skin up to the opening 512. After an
appropriate period of time, which is typically pre-set by the programmer
of the electronics, the lancing assembly 508 is triggered, thereby causing
the lancet 516 to penetrate the skin that has risen up to the opening 512
and that is engorged with blood. The lancet 516 is preferably triggered
automatically, by a solenoid valve (not shown) that causes a
vacuum-actuated piston (not shown) to trigger the lancet 516. The
remaining steps of the process relating to collection of a sample of blood
are substantially similar to the steps described in the embodiment shown
in FIGS. 1, 2, 3, and 4.
In the embodiment shown in FIG. 9, the glucose detector 514 is inserted
into a slot 518 of the housing 502. The results obtained from the glucose
detector 514 can be displayed on screen 520, typically a conventional
liquid crystal digital display. The cover portion 502a is opened when the
lancet 516 or glucose detector 514 is being replaced. The cover portion
502a is closed during the process of obtaining a sample of blood.
The relative positions of the vacuum pump, the battery, the electronics,
the switch, the evacuation tube, the check valve, the solenoid valves, and
the vacuum-actuated piston are substantially similar to the relative
positions of these components as described in the embodiments shown in
FIGS. 1 and 2.
In FIG. 10, blood extraction device 600 comprises a housing 602. The
housing 602 comprises a cover portion 602a that is attached to the
remaining portion 602b of the housing 602 by a hinge 606. A gasket 607 is
provided to seal the housing 602 when the cover portion 602a is closed.
The cover portion 602a can be closed by pivoting it around the hinge 606.
When the cover portion 602a is closed, edges 602c of the cover portion
602a tightly fit against edges 602d of the remaining portion 602b of the
housing 602. Disposed within the housing 602 are a vacuum pump (not
shown), a lancing assembly 608, a battery (not shown), and electronics
(not shown). A switch 609 is provided to activate the electronics. The
vacuum pump is connected to the lancing assembly 608 by an evacuation tube
(not shown). A check valve (not shown) is placed between the vacuum pump
and the lancing assembly 608.
During the process of obtaining the sample, the cover portion 602a is
closed. The cover portion 602a of the housing 602 of the device 600 that
contacts the skin is equipped with a seal 611. The seal 611 surrounds an
opening 612 in the cover portion 602a. The opening 612 in the cover
portion 602a allows communication between the surface of the skin and a
blood extraction chamber adjacent to a glucose detector 614, shown here in
the shape of a strip. When in use, the device 600 is positioned so that
the lancing assembly 608 is placed over the region on the surface of the
skin from which the sample is to be obtained. In order to obtain the
sample of blood, the cover portion 602a of the housing 602 of the device
600 is placed against the skin, whereby the seal allows a satisfactory
vacuum to be effected. The switch is actuated, typically by being pressed,
thereby activating the electronics, which starts the vacuum pump. The
vacuum pump then provides a suction action. The suction action of the
vacuum pump causes the skin circumscribed by the seal to become engorged
with blood. Engorgement of the skin with blood is accompanied by a
stretching of and rising up of the skin up to the opening 612. After an
appropriate period of time, which is typically pre-set by the programmer
of the electronics, the lancing assembly 608 is triggered, thereby causing
the lancet 616 to penetrate the skin that has risen up to the opening 612
and that is engorged with blood. The lancet 616 is preferably triggered
automatically, by a solenoid valve (not shown) that causes a
vacuum-actuated piston (not shown) to trigger the lancet 616. The
remaining steps of the process relating to collection of a sample of blood
are substantially similar to the steps described in the embodiment shown
in FIGS. 1, 2, 3, and 4.
In the embodiment shown in FIG. 10, the glucose detector 614 is inserted
into a slot 618 of the housing 602. The results obtained from the glucose
detector 614 can be displayed on screen 620, typically a conventional
liquid crystal digital display. The cover portion 602a is opened when the
lancet 616 or glucose detector 614 is being replaced. The cover portion
602a is closed during the process of obtaining a sample of blood.
The relative positions of the vacuum pump, the battery, the electronics,
the switch, the evacuation tube, the check valve, the solenoid valves, and
the vacuum-actuated piston are substantially similar to the relative
positions of these components as described in the embodiments shown in
FIGS. 1 and 2.
In each of the embodiments shown in the foregoing FIGS. 5, 6, 7, 8, 9, and
10, the housing, vacuum pump, lancing assembly, battery, electronics,
evacuation tube, check valve, nosepiece, seal, opening, blood extraction
chamber, lancet, and solenoid valve can be made of the same materials as
the corresponding components of the apparatus shown in FIGS. 1, 2, and 3.
The gaskets 104, 207, 307, 407, 507, and 607 can be made of the same
material as the seal. The components shown in the foregoing FIGS. 5, 6, 7,
8, 9, and 10 function in the same manner as do the corresponding
components of the apparatus shown in FIGS. 1, 2, and 3.
It should be noted that the designs of the various housings shown in FIGS.
5, 6, 7, 8, 9, and 10 can be modified without substantially affecting the
functioning of the components disposed within the housing or on the
surface of the housing. For example, the shapes of the housings, the
shapes of the door portions of the housings, the shapes of the cover
portions of the housings, and the shapes of the remaining portions of the
housings can be modified without departing from the scope and spirit of
this invention.
This invention provides numerous advantages over blood extraction devices
of the prior art. Among these advantages are the following:
1. Ability to use parts of the body, other than the finger, as a site for
the extraction of blood;
2. Reduction of pain by eliminating the need to lance the finger;
3. Increase in speed of collection of blood samples by means of
pretreatment comprising a combination of stretching of the skin in
conjunction with heat or vacuum or both heat and vacuum;
4. Incorporation of glucose detector in apparatus for extracting the blood
sample.
The following examples illustrate various features of the present invention
but is not intended to in any way limit the scope of the invention as set
forth in the claims. In the following examples, the term "pierce" and
forms thereof and the term "puncture" and forms thereof are used
interchangeably. Although the expression "glucose detector" is used
herein, one of ordinary skill in the art will recognize that the apparatus
and methods of the present invention can also be used to perform other
diagnostic tests.
EXAMPLES
Example 1
This example illustrates that greater volumes of blood can be extracted and
collected by applying a vacuum, pulsed or continuous, after piercing than
can be extracted and collected when no vacuum is applied. No vacuum was
applied prior to piercing.
Each of four people had his forearm (dorsal forearm) punctured four times
(at four different positions on the forearm) with a "BD ULTRA-FINE" lancet
in a "MEDISENSE" lancet assembly (Model no. 97101) at two different levels
of vacuum (-2.5 psig and -5.0 psig) and for each different vacuum pulsing
frequencies (0, 0.2, 0.8, 3.2, 12.8, 25, 100 hertz). The vacuum was
applied with a pipette tip having a diameter of 8 mm ("RAININ RT-200").
Four control runs without a vacuum were also carried out (one puncture per
person). A total of 60 punctures per person were carried out. Accordingly,
it can be seen that a total of 240 runs were carried out.
The vacuum was applied for a duration of 30 seconds after puncturing. Blood
was collected into capillary tubes. In the control runs, the samples were
extracted and collected 30 seconds after puncturing. The amount of blood
collected was determined by measuring the length of blood in the tubes.
The percentage of collections in which the volume of blood collected
exceeded 1.0 .mu.L was calculated. Sensation of pain was also recorded.
The following pain scores were used:
Pain of 1=person did not feel anything or not sure if anything was felt
Pain of 2=person felt definite prick, not as painful as piercing of finger
by standard finger lancet
Pain of 3=person felt definite pain, approximately equal to a piercing of
finger by standard finger lancet
Blood collection results are set forth in TABLE I.
TABLE I
______________________________________
Average Percent of Average Percent of
volume of samples volume of
samples
blood sam-
having > 1 .mu.L
blood sam-
having >1 .mu.L
ple collect-
of blood ple collect-
of blood
Frequency
ed at -2.5
collected at
ed at -5.0
collected at
(hertz)
psig (.mu.L)
-2.5 psig psig (.mu.L)
-5.0 psig
______________________________________
0 1.6 69 3.1 94
(Conti-
nuous)
0.2 1.1 44 3.0 94
0.8 1.1 63 75
3.2 1.5 56 3.8 75
12.8 1.8 75 3.1 100
25 2.3 75 3.2 94
100 2.4 51 2.7 88
______________________________________
With no vacuum, average volume of blood collected was 0.8 .mu.and 31% of
the samples collected contained more than 1 .mu.L. The pain results we re
as follows:
pain of 1=81%
pain of 2=17%
pain of 3=2%
The control runs (no vacuum) provided much lower volumes of blood collected
than did the runs where vacuum was applied. Increased vacuum resulted in
higher volumes of blood extracted. The pain was minimal, with only 2% of
the punctures resulting in pain comparable to that resulting from a
piercing of the finger.
Example 2
This example illustrates that application of vacuum prior to piercing as
well as after piercing results in a greater volume of blood extracted than
does the application of vacuum only after piercing.
Each of four people had his forearm (dorsal forearm, middle of forearm)
punctured sixteen times (at sixteen different positions on the forearm)
with a "BD ULTRA-FINE" lancet in a modified "MEDISENSE" lancet assembly at
four different levels of vacuum. The four levels of vacuum used were -2.5,
-5.0, -7.5, and -10.0 psig. The "MEDISENSE" lancet device was modified to
allow vacuum to be pulled through the lancet assembly. Four punctures per
person were carried out at each of the four levels of continuous vacuum.
Accordingly, it can be seen that a total of 64 runs were carried out.
Prior to puncturing, the vacuum was applied for a period of 30 seconds;
subsequent to puncturing, the vacuum was applied for a period of 30
seconds. The skin was under vacuum at the time the lancet was triggered.
After the lancet was triggered, the lancet assembly was removed, and the
vacuum was used to apply the same level of vacuum that had been used for
the vacuum prior to puncturing. The vacuum, both prior to puncturing and
subsequent to puncturing, was applied with a pipette tip having a diameter
of 8 mm ("RAININ RT-200"). The pipette tip of the vacuum device was held
level to the plane of the skin. Blood was then collected into capillary
tubes. The amount of blood collected was determined by measuring the
length of blood in the tubes. The percentage of collections in which the
volume of blood collected exceeded 1.0 .mu.L was calculated. Sensation of
pain was also recorded. Blood collection results are set forth in TABLE
II.
TABLE II
______________________________________
Percent of samples
Average volume of blood
having >1 .mu.L of blood
Vacuum level (psig)
sample collected (.mu.L)
collected
______________________________________
-2.5 4.6 94
-5.0 7.8 100
-7.5 9.2 100
-10.0 14.0 100
______________________________________
The pain results were as follows:
pain of 1=58%
pain of 02=31%
pain of 3=11%
A nearly linear relationship between level of vacuum and volume of blood
collected was observed. The average volume of blood collected with vacuum
applied prior and after piercing was approximately twice that collected
with vacuum applied only after piercing without vacuum applied prior to
piercing. See the results of Example 1 for this comparison (7.8 .mu.L vs.
3.1 .mu.L). The volume of blood collected was always above 1 .mu.L for all
levels of vacuum, except -2.5 psig.
Example 3
This example illustrates that localized heating of the area to be pierced
followed by vacuum after piercing results in a greater volume of blood
being extracted than does extraction with only vacuum after piercing.
Each of four people had his forearm (dorsal forearm, middle of forearm)
punctured eight times (at eight different positions on the forearm) with a
"BD ULTRA-FINE" lancet in a "MEDISENSE" lancet assembly with heat applied
(45.degree. C.) prior to piercing for two different time periods, 15
seconds and 60 seconds. A total of 32 runs were carried out, 16 runs where
the pre-heating duration was 15 seconds and 16 runs where the pre-heating
duration was 60 seconds.
Heat was applied with a heating block, which was an aluminum block having a
square face covered with a "KAPTON" film heater element controlled by an
"OMEGA" DP41 temperature controller using a T-type thermocouple. Vacuum
was applied after each puncturing for 30 seconds at -5.0 psig. Blood was
collected into capillary tubes. The amount of blood collected was
determined by measuring the length of blood in the tubes. The percentage
of collections in which the volume of blood collected exceeded 1.0 .mu.L
was calculated. Pain was also tracked. Blood collection results are set
forth in TABLE III.
TABLE III
______________________________________
Percent of samples
Pre-piercing heating
Average volume of blood
having >1 .mu.L of blood
duration (seconds)
samples collected (.mu.L)
collected
______________________________________
15 6.91 94
60 11.6 100
______________________________________
The pain results were as follows:
pain of 1=91%
pain of 2=9%
pain of 3=0%
The average volume of blood collected using a pre-heating duration of 15
seconds was more than twice the average volume of blood collected at a
post-puncturing vacuum level of -5.0 psig., with no pre-heating. See the
results of Example 1 for this comparison (6.91 .mu.L vs. 3.1 .mu.L). The
average volume of blood collected using a pre-heating duration of 60
seconds was approximately four times the average volume of blood collected
at a post-puncturing vacuum level of -5.0 psig, with no pre-heating. See
the results of Example 1 for this comparison (11.6 .mu.L vs. 3.1 .mu.L).
Example 4
This example illustrates the effect that stretching the skin upwardly with
a vacuum has on the extraction of blood.
Each of four people had his forearm (dorsal forearm, middle of forearm)
punctured eight times (at eight different positions on the forearm) with a
"BD ULTRA-FINE" lancet in a "MEDISENSE" lancet assembly. Vacuum was
applied for a period of 30 seconds prior to puncturing at -5.0 psig using
two different vacuum fixtures. The first fixture was a 15 mm diameter
vacuum fixture (i.e., a hollow cylindrical tube) used without a net strung
across the opening of the tube. The second fixture was a 15 mm diameter
vacuum fixture (i.e., a hollow cylindrical tube) used with a net strung
across the opening of the lube. The net prevented skin from being raised
up into the vacuum fixture. The same vacuum fixture used prior to
puncturing was applied for a period of 30 seconds after puncturing. The
fixture was held level with the plane of the skin. Four punctures were
carried out per person per condition (without net, with net). Accordingly,
it can be seen that a total of 32 runs were carried out. Blood was
collected into capillary tubes. The amount of blood collected was
determined by measuring the length of blood in the tubes. The percentage
of collections in which the volume of blood collected exceeded 1.0 .mu.L
was calculated. Sensation of pain was also recorded. Blood collection
results are set forth in TABLE IV.
TABLE IV
______________________________________
Percent of samples
Average volume of blood
having >1 .mu.L of blood
Net across nosepiece
sample collected (.mu.L)
collected
______________________________________
No 5.2 87
Yes 0.6 19
______________________________________
The pain results were as follows:
pain of 1=94%
pain of 2=6%
pain of 3=0%
The magnitude of the difference in volume of blood collected and success
rates (i.e., percent of samples having >1 .mu.L of blood collected)
between the condition of stretching the skin in combination with a vacuum
and the condition of not stretching the skin in combination with a vacuum
was unexpected. The pain scores were low. This example demonstrates that
the combination of skin stretching and applied vacuum significantly
increased the volume of blood extracted.
Example 5
This example illustrates the effect the area of the extraction site has on
the volume of blood collected.
Each of four people had his forearm (dorsal forearm, middle of forearm)
punctured at 32 different positions on the forearm with a "BD ULTRA-FINE"
lancet in a modified "MEDISENSE" lancet assembly. The "MEDISENSE" lancet
assembly had been modified with a more powerful spring and a port had been
added.
Vacuum was applied for less than five seconds prior to puncturing. The
forearm was punctured under a vacuum of either -5.0 psig or -7.5 psig. The
vacuum applied was maintained for 30 seconds after puncturing. The
diameter of the pipette tip used to apply vacuum after puncturing was
varied, with diameters of 4, 6, 8, and 10 mm being used. Four punctures
per condition (diameter, vacuum level) were carried out per person.
Accordingly, it can be seen that a total of 128 runs were carried out.
Blood was collected into capillary tubes. The amount of blood collected
was determined by measuring the length of blood in the tubes. The
percentage of collections in which the volume of blood collected exceeded
1.0 .mu.L was calculated. Sensation of pain was also recorded. Blood
collection results are set forth in TABLE VA and VB.
TABLE VA
______________________________________
vacuum level = -5.0 psig
Percent of samples
Vacuum Average volume of blood
having >1 .mu.L of blood
diameter (mm)
sample collected (.mu.L)
collected
______________________________________
4 0.3 0
6 1.7 69
8 3.4 94
10 4.1 100
______________________________________
TABLE VB
______________________________________
vacuum level = -7.5 psig
Percent of samples
Vacuum Average volume of blood
having >1 .mu.L of blood
diameter (mm)
sample collected (.mu.L)
collected
______________________________________
4 0.8 25
6 3.1 94
8 3.4 81
10 6.3 94
______________________________________
The pain results were as follows:
pain of 1=89%
pain of 2=10%
pain of 3=1%
The volume of blood collected and success rates (i.e., percent of samples
having >1 .mu.L of blood collected) were found to vary directly with the
area of raised up into the device by the vacuum. A much greater volume of
skin was raised up into the larger diameter pipette tip than into the
smaller diameter pipette tips.
Example 6
This example illustrates that a plastic multiple point lancet can be used
with heat and vacuum to collect a useful amount of blood.
Each of four people had his forearm (dorsal forearm, middle of forearm)
punctured sixteen times (at sixteen different positions on the forearm)
with a Greer Derma PIK.RTM. System for allergy testing (Greer
Laboratories, Inc., Lenoir, N.C. 28645) modified to fit into a "MEDISENSE"
lancet assembly. Pre-heating was carried out at approximately 40.degree.
C. and 45.degree. C. for 15 and 60 seconds prior to puncturing. Four
punctures were carried out per condition (temperature, time) per person.
Accordingly, it can be seen that a total of 64 runs were carried out.
Heat was applied with a heating block, which comprised an aluminum block
having one face covered with a "KAPTON" film heater element controlled by
an "OMEGA" DP41 temperature controller using a T-type thermocouple and the
opposite face in contact with the larger base of a frustum of a cone made
of copper. The larger base of the frustum had a diameter of 0.50 in. The
height of the frustum was 0.50 in. The smaller base of the frustum had a
diameter of 0.35 in. The smaller base had a cylindrical opening having a
diameter of 0.125 in. The cylindrical opening had a common axis with the
frustum. The cylindrical opening reduced the heating surface of the copper
frustum. Vacuum (-5.0 psig) was applied for a period of 30 seconds after
puncturing. The vacuum in contact with the skin was formed by a pipette
tip having a diameter of 8 mm. The pipette tip was held level with the
plane of the skin. Blood was collected into capillary tubes. The amount of
blood collected was determined by measuring the length of blood in the
tubes. The percentage of collections in which the volume of blood
collected exceeded 1.0 .mu.L was calculated. Sensation of pain was also
recorded. Blood collection results are set forth in TABLE VI.
TABLE VI
______________________________________
Temperature Percent of samples
(.degree.C.)/Time
Average volume of blood
having >1 (.mu.L) of blood
(seconds) sample collected (.mu.L)
collected
______________________________________
40/15 2.4 31
40/60 2.6 50
45/15 2.3 56
45/60 5.2 81
______________________________________
The pain results were as follows:
pain of 1=100%
pain of 2=0%
pain of 3=0%
This example demonstrates that a blood extraction process employing a
multi-point plastic lancet, pre-piercing heating, skin stretching, and
post-piercing vacuum can extract at least 1 .mu.L of blood at least 50% of
the time.
Example 7
This example illustrates the effect of the size and the shape of the
nosepiece upon the volume of blood extracted.
Each of 21 volunteers was tested thirty times in the dorsal forearm by a
modified MediSense lancing assembly employing a "BD ULTRA-FINE" lancet
(Becton-Dickinson). The MediSense lancing assembly had been modified with
a port to allow a vacuum to effect suction through the lancing assembly.
The nosepieces tested in this example were screwed onto the body of a
MediSense lancing assembly in place of the conventional nosepiece. Vacuum
(-7.5 psig) was applied for 10 seconds prior to lancing. After lancing,
blood was collected for 30 seconds at -7.5 psig. The same nosepiece that
was used prior to lancing was used for blood collection. The openings
formed in the skin had a depth of 1.6 mm.
Fifteen different nosepiece assemblies were evaluated. These assemblies are
shown in FIG. 12. The diameter of the opening in the lower base of the
nosepiece (see line "ef" in FIG. 11) varied from 9.53 to 19.05 mm. The
diameter of the opening in the lower base of the nosepiece for nosepiece
assemblies 1, 2, and 3 was 9.53 mm. The diameter of the opening in the
lower base of the nosepiece for nosepiece assemblies 4, 5, 6, and 7 was
12.70 mm. The diameter of the opening in the lower base of the nosepiece
for Nosepiece assemblies 8, 9, 10, and 11 was 15.88 mm. The diameter of
the opening in the lower base of the nosepiece for nosepiece assemblies
12, 13, 14, and 15 was 19.05 mm. The rim-to-seal distances for the
nosepieces (see line "bg" in FIG. 11) varied from 1.6 mm to 6.0 mm. The
rim-to-seal distance for nosepieces 1, 4, 8, and 12 was 1.6 mm. The
rim-to-seal distance for nosepieces 2, 5, 9, and 13 was 3.0 mm. The
rim-to-seal distance for nosepieces 3, 6, 10, and 14 was 4.5 mm. The
rim-to-seal distance for nosepieces 7, 11, and 15 was 6.0 mm.
The nosepieces shown in FIG. 12 had seals made from Buna N rubber. The
thickness of the seals (see line "eh" in FIG. 11) was 1.6 mm and the width
of the sealing surface (see line "hj" in FIG. 11) was 3.1 mm. The
nosepieces had vertical walls.
Two tests were conducted per nosepiece assembly per volunteer. Blood was
collected into capillary tubes. The amount of blood collected was
determined by measuring the distance the blood travelled into the tube.
The average amount of blood collected for each of the fifteen assemblies
and the percentage of collections in which the amount of blood exceeded
1.0 .mu.L was calculated. The results are set forth in TABLE VII.
TABLE VII
______________________________________
Average volume of blood
Percentage having >1
Nosepiece number
collected (.mu.L)
.mu.L of blood collected
______________________________________
1 3.07 95
2 4.96 100
3 7.07 95
4 2.96 95
5 6.24 100
6 13.22 100
7 16.18 95
8 3.13 83
9 4.26 86
10 8.26 98
11 9.45 98
12 2.94 76
13 3.42 86
14 5.09 98
15 9.80 100
______________________________________
The volume blood collected and the percentage of collections exceeding 1
.mu.L were both affected by the diameter of the opening in the lower base
of the nosepiece and the rim-to-seal distance of the nosepiece. Large
increases in the volume of blood collected were seen with nosepiece
assemblies 6 and 7.
Example 8
This simple illustrates the effect of tapering the interior wall of the
nosepiece and the time to draw blood from a person.
Glucose detectors in the form of multiple-layer elements comprising the
following layers from, top to bottom, were prepared:
(1) meter-contactable layer
(2) detecting layer
(3) overcoat layer
(4) blood-transporting layer
(5) covering layer
The arrangement of the layers is shown schematically in FIGS. 11A and 11B
of copending application entitled METHOD AND APPARATUS FOR OBTAINING BLOOD
FOR DIAGNOSTIC TESTS, Attorney's Docket No. 6005.US.P2, filed on evendate
herewith, the entirety of which is incorporated herein by reference.
However, the overcoat layer is substantially coplanar with the
blood-transporting layer as shown in FIG. 18 of Attorney's Docket No.
6005.US.P2.
The use of a nosepiece with a detector is shown in FIGS. 13A, 13B, 13C, and
13D. The detector 1302 was placed below the lancing assembly 1304 with the
openings in the detector aligned with the lancet 1306. The detector 1302
was placed between a lancet stop 1308 that contained an opening 1309
(shown in phantom) and a nosepiece assembly 1310. The nosepiece assembly
included a nosepiece 1311 and a seal 1312 that contacted the skin "S". The
lancing assembly 1304 prior to the application of vacuum is shown in FIG.
13A. The nosepiece assembly was placed against the forearm of a volunteer.
After application of vacuum (-7.5 psig), the skin was stretched up near to
or into contact with the detector as shown in FIG. 13B. The vacuum was
applied for a sufficient amount of time (5 seconds) to cause the blood in
the skin inside the nosepiece to pool. The lancet was then fired through
the openings in the lancet stop and the detector, as shown in FIG. 13C.
The lancet penetrated the skin. The lancet was then retracted as shown in
FIG. 13D. The blood emerged from the opening formed in the skin, assisted
by the vacuum and the stretching of the skin. The vacuum aided in the
extraction of blood until the blood reached the blood-transporting layer.
The blood "B" was then transported along the blood-transporting layer
until it reached the detecting layer of the multiple-layer element. When
the blood reached the detecting layer of the multiple-layer element, an
electrical current was generated. This current was used to determine when
to release the vacuum, and the skin came away from the nosepiece. The
detector could then be used to analyze the blood for an analyte such as
glucose.
It should be noted that the lancet stop is optional. The detector itself
can be used to stop the lancet. If the detector is used to stop the
lancet, the thickness of the detector is important, because it will
determine the depth of penetration of the lancet.
The type of multiple-layer element used in this example had one opening in
the meter-contactable layer, as shown in FIGS. 11A and 11B of Attorney's
Docket No. 6005.US.P2.
Five varieties of nosepieces were used in this example. These nosepieces
are shown in cross-section in FIG. 14. The nosepieces varied in the areas
of the opening in the upper base, and the distance from the lower base at
which tapering of the interior wall began. The diameters "d" of the
openings in the upper base for each nosepiece was as follows:
______________________________________
Diameter of opening in
Nosepiece upper base (mm)
______________________________________
A 12.7
B 3
C 6
D 3
E 6
______________________________________
The rim-to-seal distance (see line "bg" in FIG. 11), 4.5 mm, and the
diameter of the opening in the lower base of the nosepiece (see line "ef"
in FIG. 11), 12.7 mm, was the same for all five nosepieces. The nosepiece
assemblies shown in FIG. 14 had seals made from Buna N rubber, 40A
durometer hardness. The thickness of the seals (see line "eh" in FIG. 11)
was 1.6 mm, and the width of the sealing surface (see line "hj" in FIG.
11) was 3.1 mm
Eight volunteers were tested as described above. Each volunteer was tested
10 times with nosepiece A and four times with each of the remaining
nosepieces, B, C, D, and E in FIG. 14. The time required for the
multiple-layer element to fill was recorded. The element was considered
filled when a current of 1.5 microamperes (.mu.A) was generated by the
element. The vacuum was then released. The average time required to reach
1.5 .mu.A for each nosepiece was calculated and is shown in FIG. 15. The
smaller the diameter of the opening in the upper base, the less time was
required to fill the detector.
Example 9
This example illustrates the effect of tapering the interior wall of the
nosepiece upon the time to draw blood and the success of drawing blood
from a volunteer from whom drawing blood was typically difficult.
The experiment was conducted as described in Example 8 with the following
exceptions. Only nosepieces having the configurations of nosepieces A and
B were used in the example. The diameter of the opening in the upper base
on nosepiece B was four millimeters instead of the three millimeter
opening used in Example 8. The volunteer was tested 10 times using
nosepiece A. The volunteer was also tested 10 times with nosepiece B. The
average time required to fill the multiple-layer element was calculated
for elements that filled in 40 seconds or less and is shown in FIG. 16.
The percentage of multiple-layer elements that filled in 40 seconds or
less was calculated and is shown in FIG. 17.
The nosepiece having the opening in the upper base having a diameter of
less than the diameter of the opening in the lower base, nosepiece 13,
filled in less than half the time required by a nosepiece where the
diameter of the opening in the upper base was equal to the diameter of the
opening in the lower base, nosepiece A. The percentage of multiple-layer
elements that were filled in under 40 seconds was significantly improved
for nosepiece B, as compared with nosepiece A.
Example 10
This example illustrates the effect of the shape of the opening in the
upper base upon the time required to draw blood from a person.
Glucose detectors in the form of multiple-layer elements comprising the
following layers, from top to bottom, were prepared:
(1) meter-contactable layer
(2) detecting layer
(3) overcoat layer
(4) blood-transporting layer
(5) covering layer
The arrangement of the layers is shown schematically in FIGS. 11A and 11B
of copending application entitled METHOD AND APPARATUS FOR OBTAINING BLOOD
FOR DIAGNOSTIC TESTS, Attorney's Docket No. 6005.US.P2, filed on evendate
herewith, the entirety of which is incorporated herein by reference.
However, the overcoat layer is substantially coplanar with the
blood-transporting layer as shown in FIG. 18 of Attorney's Docket No.
6005.US.P2.
The use of a nosepiece with a detector is shown in FIGS. 13A, 13B, 13C, and
13D. The detector 1302 was placed below the lancing assembly 1304 with the
openings in the detector aligned with the lancet 1306. The detector 1302
was placed between a lancet stop 1308 that contained an opening 1309
(shown in phantom) and a nosepiece assembly 1310. The nosepiece assembly
1310 included a nosepiece 1311 and a seal 1312 that contacted the skin
"S". The lancing assembly 1304 prior to the application of vacuum is shown
in FIG. 13A. The nosepiece assembly 1304 was placed against the forearm of
a volunteer. After application of vacuum (-7.5 psig), the skin was
stretched up near to or into contact with the detector as shown in FIG.
13B. The vacuum was applied for a sufficient amount of time (5 seconds) to
cause the blood in the skin inside the nosepiece to pool. The lancet was
then fired through the openings in the lancet stop and the detector, as
shown in FIG. 13C. The lancet penetrated the skin. The lancet was then
retracted, as shown in FIG. 13D. The blood emerged from the opening formed
in the skin, assisted by the vacuum and the stretching of the skin. As
quickly as possible, the multiple-layer element was slid approximately 2
mm in the direction away from the electrical contacts. This type of
movement is more fully described in copending application entitled METHOD
AND APPARATUS FOR OBTAINING BLOOD FOR DIAGNOSTIC TESTS, Attorney's Docket
No. 6005.US.P4, filed on evendate herewith, the entirety of which is
incorporated herein by reference. The vacuum aided in the extraction of
blood until the blood reached the blood-transporting layer. The blood "B"
was then transported along the blood-transporting layer until it reached
the detecting layer of the multiple-layer element. When the blood reached
the detecting layer of the multiple-layer element, an electrical current
was generated. This current was used to determine when to release the
vacuum, and the skin came away from the nosepiece. The detector could then
be used to analyze the blood for an analyte such as glucose.
It should be noted that the lancet stop is optional. The detector can be
used to stop the lancet. If the detector is used to stop the lancet, the
thickness of the detector is important, because it will determine the
depth of penetration of the lancet.
The type of multiple-layer element used in this example had two openings in
the meter-contactable layer, as shown in FIG. 16A of Attorney's Docket No.
6005.US.P2.
A pneumatic lancing assembly was used to fire the lancet. The pneumatic
lancing assembly was the type of lancing assembly described in FIGS. 16
and 17 of copending application entitled METHOD AND APPARATUS FOR
OBTAINING BLOOD FOR DIAGNOSTIC TESTS, Attorney's Docket No. 6005.US.P1,
filed on evendate herewith, the entirety of which is incorporated herein
by reference.
Five variations of nosepiece assemblies were used in this example. They are
shown in top view and cross section in FIG. 18. The nosepieces varied in
the depth of the rim (see line "ab" in FIG. 11) and the shape of the
opening in the upper base. The rim-to-seal distance plus the depth of the
rim, 4.0 mm, (see line "bg" plus line "ab" in FIG. 11) and the diameter of
the opening in the lower base of the nosepiece, 12.7 mm, (see line "ef" in
FIG. 11) was the same for all five nosepieces.
Eight volunteers were tested on the dorsal forearm as described above. Each
volunteer was tested four times with each of the five nosepieces, for a
total of 20 tests per volunteer. The time for the detector to fill after
lancing was recorded. The detector was considered filled when a current of
1.5 .mu.A was generated. The vacuum was then released. The average time
required to reach a current of 1.5 .mu.A for the five nosepieces was
calculated and is shown in TABLE VIII.
TABLE VIII
______________________________________
Shape of opening
Average time to
Nosepiece
Depth of rim (mm)
in upper base
reach 1.5 .mu.A (sec)
______________________________________
A 0.38 Circle 7.6
B 0.76 Circle 11.6
C 0.76 Circle 13.5
D 0.76 Oval 8.6
E 1.3 Oval 12.6
______________________________________
The nosepieces as shown in FIG. 18 had seals made from Buna N rubber, 40A
durometer. The thickness of the seal (see line "eh" in FIG. 11) was 1.6 mm
and the width of the sealing surface (see line "hj" in FIG. 11) was 3.1
mm.
For a given opening shape, the nosepieces having rims of lower depth
required less time to fill the detector than did those nosepieces having
rims of greater depth. For a given depth of rim, the nosepieces having
oval rim openings required less time to fill the detector than did
nosepieces having circular rim openings.
Example 11
This example illustrates the effect of different sealing materials upon the
ability to form a good vacuum seal to a hairy arm.
Seals were punched out from sheets of different sealing materials. The
eight materials used are listed in TABLE IX. The seals, which were
circular in shape, had a sealing surface width (see line "hj" in FIG. 11)
of 3.1 mm. Each seal was then utilized in a nosepiece, as shown in FIG.
11. The seals were attached to the lower base of the nosepiece by means of
an adhesive. The distance from the rim to the lower base of nosepiece
prior to attachment of the seal was 1.5 mm. After the attachment of the
seal, the rim-to-seal distance of the nosepiece was variable due to the
differences in the thickness of the seal.
A vacuum port was attached to the nosepiece to allow a vacuum source to
effect suction through the nosepiece. An air flow meter (Alicat
Scientific, Tucson, Ariz., Model #PVM200SCCM-D-S-A) was attached between
the vacuum source and the nosepiece. The nosepiece was attached to a
holder. The combined weight of the nosepiece and holder was 230 grams. A
male volunteer who had more hair on his dorsal forearm than did the
average male population was chosen. The volunteer placed his arm against
the seal of the nosepiece so as to bring the full weight of the nosepiece
and holder against the arm. The purpose of this apparatus was to provide a
constant pressure. A vacuum of -8 psig was applied. The ability of the
seal to seal to the skin was measured by the amount of air leaking into
the nosepiece, as measured by the air flow meter in the units of standard
cubic centimeters per minute (SCCM). The measurement was repeated at a
total of 20 locations on the volunteer's forearm for each of the seal
types. The average leakage rate at the twenty forearm sites for each of
the seal materials is shown in FIG. 19.
All the materials were capable of limiting the average leakage rate to
below 40 SCCM on the volunteer. The leakage rate is important because the
size of the vacuum pump required is directly proportional to the leakage
rate. In addition, a low leakage rate will result in improved battery
life. A small vacuum pump can be used at a low leakage rate. The low
leakage rates obtained allow a commercially available miniature vacuum
pump, such as that available from T-Squared Manufacturing Company, Nutley,
N.J., and having the part number T2-03.08.004, to be used with the
apparatus. The low leakage rates obtained with the seal materials tested
mean that cumbersome methods of attaching the nosepiece to the skin to
achieve a good seal are not needed. Other methods to attach the nosepiece
to the skin to form a vacuum seal are not preferred. An adhesive is not
preferred because it will make the nosepiece assembly difficult to remove,
and it can cause pain to the user when the seal is removed. Grease is not
preferred because it will leave a residue after the test is complete.
TABLE IX
______________________________________
Thickness
Seal no.
Material Manufacturer/Supplier
(mm)
______________________________________
1 silicone rubber,
McMaster Carr, #8632K921
1.6
50A durometer
6 neoprene/SBR/EP
Jessup Mfg. 3.2
DM blend foam
12 silicone rubber
unknown 1.6
16 neoprene, 5-10A
McMaster Carr, #8639K512
1.6
durometer
17 Buna-N rubber,
McMaster Carr, #86715K102
1.6
40A durometer
32 chlorinated Ashland Rubber, #90-5271
1.9
polyisoprene
35 neoprene Pres-On Corp., #p-8100
3.2
41 rubber Standard Rubber Company,
1.6
#4119N/SCE-41
______________________________________
Example 12
This example illustrates the effect of different sealing materials upon the
amount of blood extracted from a person.
Each of four volunteers was tested 32 times in the dorsal forearm by a
modified MediSense lancing assembly employing a "BD ULTRA-FINE" lancet.
The MediSense lancing assembly had been modified with a port to allow a
vacuum to effect suction through the lancing assembly. The nosepieces
tested in this example were screwed onto the body of a MediSense lancing
assembly in place of the conventional nosepiece. Vacuum (-7.5 psig) was
applied for five seconds prior to lancing. Blood was collected after
lancing for 30 seconds at -7.5 psig using the same nosepiece as was used
prior to lancing. The depth setting of the lancet was 1.6 mm. Eight
different nosepiece assemblies were evaluated Four tests were conducted
per nosepiece assembly per volunteer. Blood was collected into capillary
tubes. The amount of blood collected was determined by measuring the
length of blood in the tube. The average amount of blood collected for
each of the eight nosepiece assemblies is shown in FIG. 20.
For the eight different nosepiece assemblies, the diameter of the opening
in the base (see line "ef" in FIG. 11) was 10 mm, the diameter of the
opening in the upper base (see line "cd" in FIG. 11) was 4 mm, the
rim-to-seal distance (see line "bg" in FIG. 11) was 3 mm, and the width of
the sealing surface (see line "hj" in FIG. 11) was 3.1 mm. The nosepiece
assemblies differed in the material used for the nosepiece seal and the
thickness of the seal. The eight variations of sealing material and
thicknesses thereof are listed in TABLE X.
TABLE X
______________________________________
Nose- Thick-
piece ness
no. Sealing material
Manufacturer/Supplier
(mm)
______________________________________
1 Buna N, 40A durometer
McMaster Carr, #86715K102
1.6
2 Buna N, 40A durometer
McMaster Carr, #86715K102
3.2
3 Buna N, 60A durometer
McMaster Carr, #86305K421
1.6
4 sorbothane Sorbothane Inc. 1.6
5 sorbothane, siliconized
Sorobothane Inc., siliconized
1.6
by Applied Membrane
Technology
6 neoprene, 5-10A
McMaster Carr, #8639K512
1.6
durometer
7 closed cell toam
UFP Technology, #G-231N
1.6
8 neoprene/SBR/EPDM
Jessup 3.2
blend foam
______________________________________
All of the eight different nosepiece seal materials sealed well enough to
the skin to enable the extraction of on average greater than 3 .mu.L of
blood in 30 seconds. The hardest material of the eight tested, Buna N-60A
durometer, had the highest blood extraction rate. Increasing the seal
thickness from 1.6 to 3.2 mm had little effect on the volume of blood
collected in 30 seconds.
Example 13
This example illustrates the effect of using a novel seal upon the time
required to extract blood from a person.
Glucose detectors in the form of multiple-layer elements comprising the
following layers, from top to bottom, were prepared:
(1) meter-contactable layer
(2) detecting layer
(3) overcoat layer
(4) blood-transporting layer
(5) covering layer
The arrangement of the layers is shown schematically in FIGS. 11A and 11B
of copending application entitled METHOD AND APPARATUS FOR OBTAINING BLOOD
FOR DIAGNOSTIC TESTS, Attorney's Docket No. 6005.US;.P2, filed on evendate
herewith, the entirety of which is incorporated herein by reference.
However, the overcoat layer is substantially coplanar with the
blood-transporting layer as shown in FIG. 18 of Attorney's Docket No.
6005.US.P2.
The use of a nosepiece with a detector is shown in FIGS. 13A, 13B, 13C, and
13D. The detector 1302 was placed below the lancing assembly 1304 with the
openings in the detector aligned with the lancet 1306. The detector 1302
was placed between a lancet stop 1308 that contained an opening 1309
(shown in phantom) and a nosepiece assembly 1310. The nosepiece assembly
1310 included a nosepiece 1311 and a seal 1312 that contacted the skin
"S". The lancing assembly 1304 prior to the application of vacuum is shown
in FIG. 13A. The nosepiece assembly was placed against the forearm of a
volunteer. After application of vacuum (-7.5 psig), the skin was stretched
up near to or into contact with the detector as shown in FIG. 13B. The
vacuum was applied for a sufficient amount of time (5 seconds) to cause
the blood in the skin inside the nosepiece to pool. The lancet was then
fired through the openings in the lancet stop and the detector, as shown
in FIG. 13C. The lancet penetrated the skin. The lancet was then
retracted, as shown in FIG. 13D. The blood emerged from the opening formed
in the skin, assisted by the vacuum and the stretching of the skin. The
vacuum aided in the extraction of blood until the blood reached the
blood-transporting layer. The blood "B" was then transported along the
blood-transporting layer until it reached the detecting layer of the
multiple-layer element. When the blood reached the detecting layer of the
multiple-layer element, an electrical current was generated. This current
was used to determine when to release the vacuum, and the skin came away
from the nosepiece. The detector could then be used to analyze the blood
for an analyte such as glucose.
It should be noted that the lancet stop is optional. The detector itself
can be used to stop the lancet. If the detector is used to stop the
lancet, the thickness of the detector is important, because it will
determine the depth of penetration of the lancet.
A pneumatic lancing assembly was used to fire the lancet. The pneumatic
lancing assembly was the type of lancing assembly described in FIGS. 11,
12, 13, and 14 of copending application entitled METHOD AND APPARATUS FOR
OBTAINING BLOOD FOR DIAGNOSTIC TESTS of Attorney's Docket No. 6005.US.P1,
filed on evendate herewith, the entirety of which is incorporated herein
by reference.
The type of multiple-layer element used in this example had one opening in
the meter-contactable layer, as shown in FIGS. 11A and 11B of Attorney's
Docket No. 6005.US.P2.
Two nosepiece assembly variations were used in this example. The size and
structure of both nosepieces in the nosepiece assemblies were the same as
that of nosepiece B of FIG. 14, with the exception that the diameter of
the opening in the upper base was increased to 4 mm. One nosepiece had a
planar Buna N seal, 40 durometer (see FIG. 11). The other nosepiece had a
seal of the type shown in FIGS. 21A and 21B in cross section, referred to
hereinafter as a flex seal. The flex seal contacts a larger area of skin
then does a planar seal. The flex seal can then cause more skin to be
brought into the internal space of the nosepiece when vacuum is applied
than can a planar seal. The flex seal was made out of a silicone, 40A
durometer.
The flex seal 3020 can be attached to the nosepiece 3022 by a mechanical
attachment 3024 or by an adhesive. The portion 3026 of the flex seal that
is not attached to the nosepiece 3022 is capable of moving between a first
position, as shown in FIG. 21A, and a second position, as shown in FIG.
21B. In the first position, the unattached portion 3026 of the flex seal
3020 depends from the lower base 3028 of the nosepiece 3022 as shown in
FIGS. 21A. In the second position, the unattached portion 3026 of the flex
seal 3020 contacts the lower base 3028 of the nosepiece 3022 such that one
major surface of the unattached portion of the seal is in face-to-face
contact with the lower base 3028 of the nosepiece as shown in FIG. 21B.
The flex seal is made of a material having a coefficient of friction that
reduces the tendency of skin in contact with it to slide. The seal should
be sufficiently flexible so that it can move between the first position
and the second position and sufficiently stiff to hold the skin in an
immovable position. The opening 3030 in the flex seal has an area greater
than the area of the opening 3032 in the lower base 3028 of the nosepiece
3022, when the flex seal is in the first position, as shown in FIG. 21A.
In operation, the flex seal, is placed against the skin "S" of the patient.
The area of skin contacted by the flex seal is greater than the area of
the opening in the lower base of the nosepiece. Consequently, the volume
of skin lifted into the nosepiece is greater than the volume of skin that
would have been lifted into the nosepiece with a planar seal. Thus, the
flex seal would be beneficial for a patient having below normal skin
flexibility.
Eight volunteers were tested on the dorsal forearm substantially in the
manner described previously. In the previous examples, the nosepiece
assembly was manipulated by moving it from side to side or toward and away
from the skin. In this example, the nosepiece assembly was not moved after
it was placed against the skin. Each volunteer was tested eight times
using the planar seal and flex seal configurations for a total of 16 tests
per volunteer. The time to fill the detector after lancing was recorded.
The detector was considered filled when a current of 1.5 .mu.A was
generated. The vacuum was then released. The average time required for the
current to reach 1.5 .mu.A for the flex seal was 14.9 seconds and the
average time required for the current to reach 1.5 .mu.A for the planar
seal was 17.9 seconds.
The nosepiece employing the flex seal required less time to fill the
detector than did the nosepiece employing a planar seal. Moreover,
manipulation of the nosepiece assembly was eliminated.
Various modifications and alterations of this invention will become
apparent to those skilled in the art without departing from the scope and
spirit of this invention, and it should be understood that this invention
is not to be unduly limited to the illustrative embodiments set forth
herein.
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